Abstract: According to the actual characteristics of our plant, the actual situation, size and characteristics of the geological environment of operation and maintenance, and introduced the ground or take zero protection, leakage protection three kinds of leakage protection mode,glue stick on the principle of leakage protection, classification, Xuan Yong installation principles and operation of common faults were studied in detail.
Keywords: Electrical equipment grounding, then zero, and leakage protection principle of operation
First,glue gun the need for earth leakage protection. Ground fault protection, also known as protective ground (safety ground), is the metal casing of electrical equipment and grounding connections, electrical equipment insulation damage to shell when charged directly into the earth fault current to avoid contact with the operator from electrical shock and equipment enclosure. Leakage protection device is a fatal electric shock hazards to provide indirect contact protection, because of its Yi leakage current or arising out of neutral to ground voltage for the output signals, so do not have to electric current value to the value of setting action, sensitivity high, action is able to effectively cut off the power, to protect personal safety.
Second, protection of ground and then zero. Construction Site and access to Ground Zero which means the way the power supply with on-site: (a) of the neutral ground of non-direct low-voltage power supply network, low-voltage electrical installations should be grounded to protect. (B) in the neutral grounding of low voltage power supply network, low-voltage electrical installations should be connected with zero protection, and sometimes directly in the neutral ground of three-phase four-wire TN-C network and do protect the neutral ground PEN repeat equipment enclosure to reduce the leakage to ground voltage; alleviate the disruption caused by the neutral risk of electric shock; the protection of the neutral line of cross section with cross section of not less than 50%, and as far as possible with the same phase line. (C) use of dedicated low-voltage power supply transformer, the electrical installations should be neutral grounding of the three-phase five-wire system (TN-S) protective zero system - metal casing of electrical equipment with special protection must be zero line (PE) and reliable connection; special protection of the zero line for the working ground wire, power distribution room (box-type transformer) of the zero line or first-class power supply side leakage protection leads to the zero line. (D) protection of ground and then the principle of zero. 1, protective grounding principles. In the neutral point ungrounded low-voltage systems, electrical building needs under normal circumstances, the various electrical devices do not live exposed parts of metal, power supply equipment enclosure should be grounded (special exceptions). (1) motors, transformers, portable or mobile electrical appliances in the metal base and shell. (2) the transmission of electrical equipment. (3) power distribution, control, protection of the screen (cabinet, box iron system distribution box), and welding, welder's operation platform, the metal frame and base. (4) gasoline, diesel, engine oil tank shell. (5) 20m above the shaft frame (such as a central chimney construction derrick, the Electric Lifting / L-mode devices) scaffolding tower construction boom crane used for lifting off, the lift curve track. (6) installed in the power line tower on the electrical equipment enclosure and bracket. (7) Crane (electric hoist, gantry crane, DBQ series of tower cranes, etc.) 2 points for each track should be set ground. Joints between the track, should make electrical connections; grounding resistance should be less than 4Ω. When equipped with a ground slide adapter, slide adapter slide and rail or ground wire connection to be reliable. Crane driver's cab and body with a screw connection, the electrical jumper should be, its cross-contacts should not be less than 2: Cross-connected should adopt the multi-strand copper wire, the cross section area of not less than 16mm2, both ends of the crimping terminal should be galvanized screw fixation; when using round or flat cross-connected, the round diameter of not less than 12mm, the width and thickness of flat steel section shall not be less than 40mm, 4mm.
2, protective zero principles. (1) Under normal circumstances, the construction site of the following electrical equipment not charged exposed conductive parts should be done to protect access zero. ① motors, transformers, lighting appliances, electric tools, metal hand. ② electrical equipment gear metal parts. ③ power distribution panel and control panel of the metal frame. ④ indoor and outdoor distribution equipment near live parts of metal frame and metal fences and metal gates. ⑤ power line metal protection tube and wrap-line cable, crane rail sliding metal template operating platforms. ⑥ installed in the power pole line switches, capacitors and other electrical equipment and metal stents. ⑦ poor conditions or humid places (such as the boiler room, dining room, basement and bathroom, cable tunnels) to protect connected electrical equipment must be zero.
(2) Note. Zero line in the laying of protection, the protection of the zero line should be a separate installation, not to use it; protection of the zero line may not be installed switch or fuse. Especially in the construction of power line shared with the foreign power systems, electrical equipment should be based on the requirements of the local power company or the protection of access with protection of ground zero; in by the same generator, the same transformer or the same bus-powered low-voltage power network , should not also use ground zero protection and access protection.
4, leakage protection installation and use. Leakage current protective device referred to as leakage protection device, also known as leakage protection switches, mainly used in the device causes a short circuit failure and the risk of a fatal electric shock to protect themselves. (A) the principle of leakage protection. Leakage protection device is the use of residual current system of response and action, normal operation of the system of residual current is almost zero, and therefore considered the setting value moves a block to be very Xiao (General 为 mA level), when the system Fasheng personal electric shock or Shebei shell When charged, a larger residual current leakage protection is by detecting and dealing with this residual current is reliably move, cut off power supply. (B) leakage protection classification. Leakage protection can be protected according to their function, structural features, installation, operation mode, number of poles and lines, movement sensitivity classification, where the main function and purpose of their protection classification described, generally divided into leakage protection relays, earth leakage protection switching and leakage protection socket of three.
(C) the selection of the principle of leakage protection. 1. Buy leakage protection when buying products with the production of qualified manufacturers and product quality inspection qualified. 2. Should be under protection, personal equipment, safety and environmental requirements to determine leakage protection supply voltage, operating current, leakage current and operating time of a few. 3. The power to do with leakage protection grade protection, should meet, the lower switching selectivity. Generally, a leakage protection is not less than the rated leakage current leakage protection under a rated leakage current, both to protect sensitive personal and equipment safety, but also to avoid Trip to narrow the scope of the accident check. 4. Hand-held power tools (except for outside class III), mobile consumer electronics devices used in daily life (except for outside class III), other mobile electrical equipment, as well as relatively high risk of electric shock electrical equipment must be installed leakage protection. 5. Building construction sites, temporary lines, electrical equipment, leakage protection devices should be installed. This is the "Construction Site Temporary Electrical Safety Specifications" (JGJ46-88) clearly required. 6. Offices, schools, businesses, residential buildings in the outlet circuit, hotels, restaurants and guest houses, rooms outlet circuit, electric leakage protection device must be installed. 7. Installed in the water supply lines and equipment as well as humidity, temperature, metal and other conductive occupy a larger coefficient of good places, such as mechanical processing, metallurgy, textile, electronics, food processing industry, workplace, and the boiler room, pump room, dining room, bathroom, hospitals and other places, must be used to protect leakage protection. 8. Fixed-line production of electrical equipment and normal operating areas, leakage protection should be used with power distribution box. Temporary use of small electrical equipment should be used in leakage protection plug (Block) or with leakage protection socket box. 9. Creepage protection device as a direct contact with the supplementary protection protection (not as the only direct contact protection) should be used in high sensitivity, rapid action type earth leakage protective device. Select the general environment operating current not exceeding 30mA, operating time less than 0.1s., These two parameters to ensure that if an electric shock when the body would not have led to an electric shock risk effect of pathological physiology. In the bathroom, swimming pool and other areas of leakage protection rated operating current not exceeding 10mA. After the shock may lead to secondary incidents of the occasion, should use the rated operating current to 6mA of leakage protection. 10. To allow the electrical power equipment, such as public places, the channel lighting, emergency lighting, fire fighting equipment, power supply, power supply for the burglar alarm, alarm should be used residual protection device connected sound, light alarm signal to inform management time dealing with failure.
Hebei Hebei peak energy peak Coking Group Co., Ltd. Safety Management (Handan, Hebei) Huangyan Hai.